Originally posted by tohax The Canon patent describes a different approach (and Canon filed the patent before Pentax published their product, so one would have to check who filed their patent first).
Pentax uses GPS, compass and level data to register the earth's axis position. Which btw is reported to not always work to full satisfaction.
Canon does a first shot and finds and analyzes the curved star trails to register the earth's axis position.
OTOH, the Canon patent assumes sensor shift SR which Canon doesn't have in their cameras. Is Canon jumping ship to sensor shift?